This paper proposes a bilateral control strategy based on pulse density modulation (PDM) and phase shift modulation (PSM) to achieve maximum efficiency point tracking (MEPT) for S-S compensated wireless power transfer (WPT) systems. Considering the parasitic resistors of coupling coils, an optimal load resistance corresponds to maximum efficiency. However, in practice, it is tough to obtain the optimal resistance due to shifty coupling coefficient and parasitic resistance. The proposed control strategy achieves MEPT precisely without calculated optimal resistance or wireless communication. For the receiving side, in different cases of input current, a semi-controlled bridge rectifier commanded by PSM is employed for stable DC output current. The transmitter adopts a control scheme which hybridizes PDM as well as perturbation and observation (P&O) method. The most efficient pulse density is selected through P&O to minimize input power, which represents the maximum efficiency. A 5-A output simulation model is established to validate the MEPT function of proposed bilateral control strategy.